J. Biol. Chem., Vol. 262, Issue 3, 1172-1179, 01, 1987
A novel group of very long chain polyenoic fatty acids in dipolyunsaturated phosphatidylcholines from vertebrate retina
MI Aveldano
Dipolyunsaturated phosphatidylcholines from bovine retina contain a whole
series of unusual fatty acids. Methyl esters from these acids are very
strongly retained on polar and nonpolar gas-liquid chromatography
stationary phases. On thin layers of silica-AgNO3, they separate as tetra-,
penta-, and hexaenoic fatty acid methyl esters. After hydrogenation, the
three polyunsaturated fractions give the same series of saturated methyl
esters, having 20 (or 22)-36 carbon atoms. High pressure liquid
chromatography, as well as gas-liquid chromatography, indicates that the
new components of the three fractions are even- carbon homologs of well
known polyenoic fatty acids of the n-6 and n-3 families, since they behave
as series of 20-36-carbon tetraenoic (n-6), pentaenoic (n-3 and n-6), and
hexaenoic (n-3) fatty acids. Their occurrence in phospholipid molecules
also having docosahexaenoate (22:6) explains the separation of major
dipolyunsaturated phosphatidylcholines from retina into dodecaenoic,
undecaenoic, and decaenoic fractions after argentation thin layer
chromatography. Using high pressure liquid chromatography, the latter are
resolved into individual species having 10-12 double bonds and 42-58 carbon
atoms. The unusual PCs are thus endowed not only with the highest degree of
unsaturation, but with the longest hydrocarbon chains yet reported for
vertebrate glycerophospholipids. It is shown that phosphatidylcholines
containing the novel fatty acids are highly concentrated in photoreceptor
membranes and that they occur in the retina of vertebrates so distant in
evolution as fish, birds, and various mammals.